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June 22, 2010 -- Blasting your iPod or another portable music player may cause temporary hearing loss, according to new research in the June issue of the Archives of Otolaryngology-Head & Neck Surgery.

“These devices are potentially harmful,” conclude the study authors, who were led by Hannah Kempler, MS, of Ghent University in Ghent, Belgium. “Further research is needed to evaluate the long-term risk of cumulative recreational noise exposures.”

Occupational noise exposure can lead to noise-induced hearing loss, but less is known about the long-term and short-term effects of recreational noise -- including exposure to loud music at a concert, on your iPod, or at noisy sporting events including the World Cup where revelers regularly blow, buzz, or honk their vuvuzela horns.

Excessive noise produces changes in the ear’s organ of Corti, which is the organ in the innerear that contains hair cells. Outer hair cells are more vulnerable to noise than inner hair cells.

In the new study, 21 participants listened to an MP3 player for a maximum of six sessions at varying volume levels using either earbuds or more traditional earphones. Researchers evaluated the participants’ hearing before and after the experiment via two standardized hearing measurements. They found that participants showed temporary changes in their hearing after listening to one hour of pop-rock music on their portable music devices.

'Shot Across the Bow'

“This paper shows without question that if you are using these devices at a high level for a long period of time, you increase your risk for temporary hearing loss,” says Brian Fligor, director of diagnostic audiology at Children's Hospital in Boston, who was familiar with the data before its publication.

“These short-term changes are reversible, but it’s the shot across the bow and there is potential to do permanent damage,” he says.

Warning signs of iPod-induced hearing loss may include ringing in the ears (tinnitus) and difficulty hearing what people are saying in a noisy room, he says. By the time the latter occurs, the damage is usually done, he tells WebMD.

“Noise-induced hearing loss sneaks up on you big time,” he says. “It’s tragic because it is completely avoidable.”

Safe iPod Rx

There are safe ways to enjoy your music on these portable devices, Fligor says. “You could listen to your iPod for an hour and a half at 80% (or a volume of level eight) and not increase your risk for hearing loss.” And, “If you keep it at six or below, you can listen all day long,” he says. These safe settings were verified by the new study.

Today’s portable music devices are capable of holding thousands of songs, and they have a much longer battery life than older devices, says Michael Rothschild, MD, director of pediatric otolaryngology at Mount Sinai Medical center in New York City.

By contrast, the Walkman of yesteryear was limited to one mixed tape in terms of the amount of music it contained, and its battery life was shorter.

This study shows that there is smoke, but it’s too early to say whether there is fire, he says.

“The fact that there is a temporary change in hearing would make one think it is worth investigating whether there is a permanent change,” Rothschild says. “Devices that have the propensity to deliver high volumes for long periods of time need to be looked into. The findings are cause for concern in the sense that every kid is carrying around in their pocket a device that could damage their hearing.”

Rothschild usually tells parents that if they can fully hear the music -- and lyrics -- through their kids’ headphones or ear buds, it is too loud.

Apple Inc., which manufactures the iPod, says the following on its web site. “if you listen to music and audio with headphones or earbuds -- whether they’re connected to your iPod, your computer, or some other audio source -- you should follow a few common-sense recommendations."

These include thinking about the proper volume setting. "Some hearing experts recommend that you set the volume while in a quiet environment, turn the volume down if you can’t hear people speaking near you, avoid turning up the volume to block out noisy surroundings, and limit the amount of time that you use earbuds or headphones at high volume," the web site states.

Keeping track of time is also important. "You can adapt to higher volume settings over time, not realizing that the higher volume may be harmful to your hearing," the web site states. “Hearing experts warn that noise-induced hearing loss can also occur as a result of repeated exposure to loud sound over time. The louder the volume, the less time required before your hearing may be affected."

The new research "helps to underscore the need for education -- teaching MP3 player users that overexposure can lead to significant effects on the ear," says Cory Portnuff, an audiologist at the University of Colorado at Boulder.

"Temporary hearing loss, like the ones identified in this study, is a big warning sign that more serious damage is occurring," Portnuff tells WebMD. "Every time that a temporary hearing loss happens in your ear, some permanent damage to the hair cells occurs.

The bottom line? "Whether it's attending a loud concert, working with power tools, or using an MP3 player, if you notice decreased hearing or ringing in the ears, you know you've had too high an exposure level."